1. Field of the Invention
The present invention relates to a method for manufacturing a variable capacity exhaust gas turbine in an exhaust gas turbocharger used for the internal combustion engine of a comparably small or medium size; whereby, the exhaust gas emitted from the engine (internal combustion) streams through a scroll passage for feeding the exhaust gas from an exhaust gas inlet to a turbine rotor, the cross-section area of the scroll passage comprising an outer scroll passage and an inner scroll passage is gradually reduced along the gas stream direction; thereby, the scroll passage is partitioned into the outer scroll passage that is placed at an outer side in the direction of the radius of the turbine rotor and the inner scroll passage that is placed at an inner side in the direction of the radius of the turbine rotor, wherein a plurality of insert vanes is provided between the outer scroll passage and the inner scroll passage so that the exhaust gas streams into the inner scroll passage not only directly from the exhaust gas inlet but also via the outer scroll passage; and, a cover that demarcates the scroll passage is provided with the insert vanes that protrude from the body surface of the cover toward the scroll passage, the insert vanes being arranged in a row along a boundary wall between the outer scroll passage and the inner scroll passage.
2. Background Art
FIG. 4(A) shows the main feature as to a cross section of a variable capacity exhaust gas turbine that is disclosed in Patent Reference 1 (JP3956884), the cross section being orthogonal to the axis of the rotation as to the gas turbine; FIG. 4(B) shows D-D cross-section in FIG. 4(A); FIG. 5 shows Y-Y cross-section in FIG. 4(A).
The variable capacity exhaust gas turbine as described above houses a turbine rotor 10 driven by the exhaust gas, in the middle part (around the rotation axis 100a) of a turbine housing of the gas turbine.
The turbine housing 01 comprises an exhaust gas inlet 20 and an exhaust gas outlet 20a; the turbine housing 01 further comprises a scroll passage through which the exhaust gas flows from an exhaust gas inlet 20 toward a turbine rotor 10 that is positioned at an inner (central) part of the housing, the cross-section of the scroll passage gradually reducing along the gas stream direction.
The scroll passage is divided into two parts; namely, the scroll passage comprises an inner scroll passage 2 and an outer scroll passage 1; between the inner scroll passage 2 and the outer scroll passage 1, a plurality of insert vanes 6a are installed in a row as the vanes are arranged along a boundary (partition) wall 2a of the scroll passage 12, in a hoop direction (a spiral direction) around the center axis of the turbine; the insert vanes 6a as well as the boundary wall play the role in partitioning the scroll passage. Further, an exhaust gas passage 6b is formed between each vane and the adjacent vane thereof.
Moreover, the multiple insert vanes 6a are provided on a cover 6 as shown in FIGS. 4 and 5; the vanes 6a are installed upright from the main body of the cover 6 along the hoop direction around the center axis of the turbine. As shown in FIG. 5, the insert vanes installed in a row separate the scroll passage 12 into the outer scroll passage and the inner scroll passage.
Further, according to Patent Reference 1 as shown in FIG. 5, a heat insulation plate 6c is integral with the cover 6; the integrated body (member) is attached between a bearing part is (of the turbine housing 01) and a bearing housing 11; namely, the integrated body is sandwiched by the turbine housing 01 and the bearing housing 11, in the neighborhood part of the outer periphery part as to the cover 6, in other words, in the neighborhood of a circular periphery 8 of the cover 6; thereby, a plurality of bolts 29 fastens the bearing housing 11 toward the turbine housing 01.
Further, as shown in FIG. 4(A), a tongue 5 is formed near the gas inlet area of the inner scroll passage 2 along the exhaust gas stream so that the exhaust gas is smoothly guided and supplied into the scroll passage 2.
Further, a control valve 4 is provided so as to control the exhaust gas flow rates into the inner scroll passage 2 as well as into the outer scroll passage 1, in a manner that the control valve 4 comes in contact with a periphery wall 4a as well as leaves the periphery wall 4a, the periphery wall 4a being formed in the turbine housing 01.
In other words, the outer scroll passage 1 is closed during the engine low-speed operation so that the control valve 4 comes into contact with the periphery wall 4a and closes (the inlet of) the outer scroll passage 1; thus, the engine exhaust gas flows only into the inner scroll passage 2 along the direction of the curved arrow U2 as shown in FIG. 4.
On the other hand, the outer scroll passage 1 is opened during the engine high-speed operation so that the control valve 4 leaves the periphery wall 4a and opens (the inlet of) the outer scroll passage 1; thus, the engine exhaust gas flows not only into the inner scroll passage 2 along the direction of the curved arrow U2 but also into the outer scroll passage 1 along the direction of the curved arrow U1 as shown in FIG. 4; further, the exhaust gas that flows into the outer scroll 1 flows into the inner scroll passage 2 through the exhaust gas passages 6b between the insert vanes 6a and the adjacent insert vanes 6a thereof.
Thus, the exhaust gas flow rate can be changed from the engine low-speed speed operation to the engine high-speed operation, and vice versa, by controlling the control valve 4.